1. Field of the Invention (Technical Field)
The present invention relates to plowing and other soil disruption devices that operate at subsurface levels.
2. Background Art
Draft-driven subsurface plows have been used for centuries, while the use of mechanically driven subsurface plows has developed more recently. By design, most subsurface plows minimize the mixing of soil layers. Subsurface plows also differ from harrows which work to break up and level surface soil. Subsurface soil plows typically operate at shallow depths, less than 1 foot, to cut shallow root systems and disrupt the hard pan or plow sole that forms beneath the blade during normal tilling operations. Crops and other vegetation with shallow root systems seldom form stable above ground structures, this allows animals and tractors to pass over in a relatively unimpeded manner. Extending subsurface plow techniques to uproot trees or vegetation with deep roots and significant above ground structure is a formidable task. No known prior patents exist on deep subsurface plows.
Subsurface plowing devices that break up the hard pan or plow sole also increase the permeability of the soil. In the Midwestern prairies, where surface soil may be only a few inches thick, subsurface plowing within the upper reaches of the clay layer breaks up the hard clay layer and increases water drainage. During this process, surface soil must not move downward nor clay upward; the goal is to disrupt a particular zone or layer only, thereby increasing overall permeability. In both of these applications, the plow does not run far below the top surface of the soil.
In mining and certain soil remediation practices, an increase in soil permeability leads to enhanced mineral recovery or soil decontamination. Unlike most agricultural situations, in mining and remediation, the relevant soil layer extends beyond the first foot of top soil. In heap-leach mining, an increase in permeability allows the leach solution to percolate deeper and faster, thereby reducing undesirable leach solution run-off. In soil remediation, an increase in permeability allows microbial degradation broth to percolate deeper and better seed the contaminated soil. For aerobic biological decontamination, the increase in permeability also leads to an increase in soil oxygenation. Increased soil oxygen levels enable aerobic microorganisms to thrive thereby speeding the decontamination process. Compaction of soil caused by truck or tractor traffic decreases permeability. Permeability also decreases when a crust forms on the surface of the soil. In both instances, ripping with a deep subsurface plow leads to an increase in soil permeability and more efficient mineral recovery or soil remediation.
Techniques have been developed for agricultural subsurface plowing, and examples appear in the following patents:
U.S. Pat. No. 1,314,394, entitled "Plow," issued on Aug. 26, 1919, to Grimes, describes a shallow subsurface plow with a specially shaped blade for harvesting peanuts and various tuberous plants. For peanut harvesting, the design allows the plow to lift and separate the peanuts from the ground.
U.S. Pat. No. 1,894,516, entitled "Brush Cutter," issued on Jan. 17, 1933, to Karstedt, describes a front mounted tractor brush cutter with a straight-edged blade fixed between two side supports. The front mounted arrangement purportedly allows the device to thrust heavier brush and young trees downward so that the tractor can pass unimpeded.
U.S. Pat. No. 1,909,752, entitled "Tree and Plant Digging Implement," filed on May 16, 1933, to Calkins, describes a U-shaped digger blade for digging young tree seedlings and plants in a manner to avoid injury to the roots. The angled blade design lifts trees and plants about four inches from their original position in the soil. This allows for most tree seedlings and all plants to be easily pulled from the ground with one hand.
U.S. Pat. No. 2,154,970, entitled "Grubbing Implement," filed on Apr. 18, 1939, to Briggs, describes a plow with a V-shaped blade to cut underground roots and aerate soil. In addition to the horizontal blade, the plow has blades on the side support arms to cut roots running horizontally and transversely to the line of movement.
U.S. Pat. No. 2,190,347, entitled "Earth Mover," issued on Feb. 13, 1940, to Austin, describes a root cutter for low growth vegetation. The cutting blade operates at a level of eight to ten inches below the ground surface.
U.S. Pat. No. 4,815,545, entitled "Subsoil Blade Ploughs," issued on Mar. 28, 1989, to Symonds, describes a plow for treating ground to improve growing conditions. The plow has both a V-shaped blade and a tyne mounted aft of the blade. The tyne breaks up a hard pan in conjunction with the swept wing blade. The effectiveness of the tyne depends on the angle with respect to the horizontal swept wing blade.
U.S. Pat. No. 5,103,918, entitled "Tillage Unit," issued on Apr. 14, 1992, to Putoni, describes a tilling plow that minimizes soil surface and soil crop residue disturbance. The depth of the plow adjusts to prevent formation of a plow sole.
Nevertheless, the need remains for a plow which beneficially disrupts subsurface soil at substantial depth without offering undue resistance to movement. In particular, a subsurface plow that disrupts a large volume of soil in a single pass through the ground is desirable, particularly in heap leach mining applications.